JPH0231830B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a passive sonar signal processing system that extracts features on frequency components from the sound of a running ship and can detect and track the sound of a particular ship while distinguishing it from others.

The schematic configuration of the conventional passive sonar device is explained in the first part.
As shown in the figure. In the figure, 1 is a receiver group, 2 is a phaser, and 3
is a square law detector, 4 is a peak detector, and 5 is a display. The receiver group 1 consists of N omnidirectional acoustic-electric transducers (receivers) spatially arranged underwater, and each receiver receives received signals X ₁ (t), X ₂ ( t)…X _N
(t) is output. The phaser 2 gives each received signal Xi(t) of the receiver group 1 a delay time according to the spatial positional relationship using a delay line, etc., and then adds all the received signals to form a directional beam. , and output an incoming signal Yθ(t) for each direction. The square law detector 3 calculates the following for the above arriving signal Yθ(t).
The square law detection shown in equation (1) is performed, and the obtained short-time power Pθ(t) is output as the signal strength at time t of the azimuth θ.

Pθ(t)=∫ ^t _tT Y ² θ(t)dt ………(1) (Here, T is the time constant of the square law detector 3.) The peak detector 4 calculates the signal strength Pθ( t)
The direction θp(t) of the peak (maximum) signal intensity is detected from the position and displayed on the display 5.

In the above configuration, the navigation sound emitted into the water by a ship sailing in the azimuth θx at time tx is received by the receiver group 1, and phased by the phasing device 2 to signal the arrival signal Yθx in the azimuth θx. (tx), and as a result, the signal strength Pθx of the direction θx output from the square law detector 3
(tx) becomes large, and the peak detector 4 detects the direction θx.
is detected and displayed on the display 5. The operator can detect the presence of a ship at the peak azimuth θx displayed on the display 5, and can monitor the movement of the ship by temporally tracking the peak azimuth.

However, in the above device, the peak is detected based on the signal strength of the sum of all frequency components included in the incoming signal for each direction output from the phaser 2, so multiple ships in close proximity or in the same direction , the weak signal strength of a ship sailing far away is masked by the high signal strength of a ship sailing nearby, making it impossible to detect its peak direction.

Figures 2 and 3 show the above situation. Figure 2 is a display example of the peak direction detected by the peak detector 4, and Figures a, b, c, and d are respectively shown in Figure 2. It shows the signal strength of the output of the square law detector 3 at times t ₁ , t ₂ , t ₃ , and t ₄ . In FIG. 2, a target B (ship) with a high signal strength is navigating in a positive direction from an approximately -22° azimuth, and a target A, a low signal strength, is navigating in a negative direction from an approximately +10° azimuth. As shown in FIG. 3a, peaks of these two targets are detected independently at time _t1 . However, at time t ₂ , goal A and goal B
Target A, which is close in direction and has low signal strength, is the third target.
As shown in Figure b, the peak cannot be detected due to the influence of the large signal strength B. After that, the peak of target A is
It intersects target B at time t ₃ and cannot be detected until time t ₄ shown in FIG. 3c. Thereafter, from time _t4 , the influence of target B decreases, and at time _t5 , the peak of target A is again detected independently, as shown in FIG. 3d. Therefore, in FIG. 2, the peak azimuth of target A is not detected at all from time t ₂ to time t ₄ .

In order to eliminate the above-mentioned conventional drawbacks, the present invention focuses on the fact that the sound of each ship has a unique frequency spectrum structure, and receives the sound of a ship using a plurality of receivers. , performs phasing processing on the output of each receiver and converts it into an incoming signal for each direction, and further analyzes the incoming signal for each direction into multiple frequency spectrum components, and calculates the frequency of a specific ship determined from the analysis results. At least one of the frequency spectrum components specific to navigation sound is added for each direction, and the direction with the maximum signal strength is determined as the peak direction. The object of the present invention is to provide a passive sonar signal processing method that can detect and track only the sound of a specific ship. The drawings will be described in detail below.

FIG. 4 is a schematic diagram of a passive sonar apparatus showing an embodiment of the present invention, and the same components as those in FIG. 1 are designated by the same reference numerals. i.e. 1
is a receiver group, 2 is a phaser, 4 is a peak detector, 5
is a display, 6 is a narrowband analyzer, 7 is a spectrum selection adder, and 8 is a display selection switch.

The narrowband analyzer 6 uses the fast Fourier transform method to further calculate short-term power spectrum densities for each frequency from the incoming signal Yθ(t) for each direction.
Pθ(f, t) is calculated and output as signal strength for each frequency at time t of azimuth θ. The spectrum selection adder 7 selects only the frequency components characteristic of the target A to be tracked and monitored from the signal strength Pθ(f, t) decomposed for each direction and frequency according to the operator's instructions, and performs the following ( 2) As shown in the formula, the calculations are totaled for each direction and the results are output as Pθ ^A (t).

Pθ ^A (t) = 〓 ^fA Pθ (f, t) ......(2) (Here, f _A is a set of frequencies characteristic of target A.) The peak detector 4 detects the orientation with respect to target A. From signal strength Pθ ^A (t) to peak direction θ ^A p(t)
is detected and displayed on the display 5. The display selection switch 8 determines whether the information to be displayed on the display 5 is the output (side) of the peak detector 4 or the output (side) of the narrowband analyzer 6 in accordance with the display selection signal instructed by the operator. This is the choice.

Next, the method of use and operation of the above device under the same target navigation conditions as in the conventional example will be explained. Fig. 5 is an example of displaying the peak direction detected by the peak detector 4, and Fig. 6 a, b, and c are each at the time points shown in Fig. 5.
The signal intensities of the outputs of the spectrum selective adder 7 at times t ₁ , _{t 2} and t _{3 , and} FIGS. There is. It is assumed here that the frequency resolution of the narrowband analyzer 6 is 1/15 of the total signal band, and the center frequencies of each band are f ₁ , f ₂ , . . . f ₁₅ .

First, in the initial state, the spectrum selection adder 7
When all frequencies, that is, (f ₁ , f ₂ ... f ₁₅ ) are specified as the selection frequency f _A of It will be output. When this state is maintained from time _t0 to time _t1 , the peak detector 4 detects both targets A and B in the same manner as in the conventional example, and displays them on the display 5 as shown in FIG.

The operator knows the existence of two targets A and B nearby from the display contents on the display 5. So at time t ₁
, the display selection switch 8 sends out a display selection signal to select the side, and the direction θ _A of the target A is determined.
The frequency spectrum of the target B and the frequency spectrum of the azimuth θ _B of the target B, that is, a and b in FIG. 7 are displayed on the display 5.

The directions θ _A and θ _B are the times of the spectrum selection adder 7.
From a in Figure 6, which shows the output at t ₁ , they are far enough apart in terms of direction that there is no leakage of each other's signals, and there are no nearby navigation targets below targets A and B, so Figure 7 a and b are considered to be spectra of the traveling sounds emitted by targets A and B, respectively.

If the intention is to track/monitor target A after time t ₁ , target B will track/monitor target A from then on.
It becomes a hindrance to monitoring. Therefore, the operator selects f ₂ and f ₇ from FIG. 7 a and b as spectra characteristic only of target A but not of target B,
After time _t1 , ( _f2 , _f7 ) is designated as the selection frequency _fA , and at the same time, the display selection switch 8 is again commanded to select the side.

Thereafter, the spectrum selection adder 7 outputs only the spectra of frequencies f ₂ and f ₇ of the signal strength for each direction to the peak detector 4. Therefore, at times t ₂ and t ₃ , only the signal of target A appears as shown in FIGS. The azimuth trajectory will be displayed. In addition, since the influence of target B is separated on the frequency axis, the azimuth trajectory of target A is
Time t ₃ when it intersects the azimuth trajectory of target B (see Figure 2)
It does not disappear even in

As described above, according to the above embodiment, since the narrow band analyzer 6 and the spectrum selection adder 7 have the ability to separate signals not only in the direction but also in the frequency range, the target B has a large signal strength in the entire frequency band. Even if there are many interfering targets nearby, if the target to be tracked has a unique spectrum that other interfering targets do not have, it can be continuously tracked and monitored.

As explained above, according to the present invention, the navigation sound of a ship is received by a plurality of receivers, the output of each receiver is subjected to phasing processing and converted into an incoming signal for each direction, and then the sound of a ship is received for each direction. The incoming signal is analyzed into a plurality of frequency spectrum components, and at least one of the frequency spectrum components unique to the running sound of a particular ship determined from the analysis results is added for each direction, and these Since the direction where the signal strength is maximum is determined as the peak direction, even if there are multiple ships (targets) in the reception area, if the directions are different, the spectral components corresponding to each target can be calculated. Therefore, its direction can be detected, and even if a specific target intersects with another target whose signal strength is higher, only the navigation sound emitted by the specific target can be heard from other targets. It has the advantage that it can be detected without being masked by the sound of the ship, and its direction can be continuously detected and tracked.

[Brief explanation of drawings]

The drawings are for explaining the present invention, and FIG. 1 is a schematic configuration diagram of a conventional passive sonar device, and FIG.
The figure is an explanatory diagram of the display output of the device in FIG. 1, FIGS. 3 a, b, c, and d are explanatory diagrams of the output of the square law detector of the device in FIG. 1, and FIGS. 4 to 7 are illustrations of the invention. 4 shows a schematic configuration diagram of a passive sonar device according to the method of the present invention, FIG. 5 is an explanatory diagram of the peak detector display output of the device in FIG. 4, and FIG. 6 a, b , c is an explanatory diagram of the output of the spectrum selective adder of the apparatus of FIG. 4, and FIG. 7 is an explanatory diagram of the output of the narrow band analyzer of the apparatus of FIG. 4. DESCRIPTION OF SYMBOLS 1... Receiver group, 2... Phaser, 4... Peak detector, 5... Display device, 6... Narrowband analyzer, 7
...Spectrum selection adder, 8...Display selection switch.

Claims (1)

[Claims] 1. Receive the sound of a ship running with multiple receivers, process the output of each receiver to convert it into an incoming signal for each direction, and then convert the incoming signal for each direction into multiple frequency spectrum components. At least one of the frequency spectrum components unique to the running sound of a particular ship determined from the analysis results is added for each direction, and the direction with the maximum signal strength is peaked. A passive sonar signal processing method characterized by determining direction.